The Comet
In the last Age of Dinosaurs (Cretaceous), mammals existed but were not a threat to dinosaur domination. It took a cataclysmic disaster to help them gain a stronger foothold. Note the herd of parrot-beaked Triceratops, one of the last dinosaurs to appear in the fossil record. The squirrel-like Crustafontia and the opossum-like Alphadon scurry for cover; it may have been their earthen burrows that saved them from annihilation at the hands of the falling comet.